Under the deal, interest rates would be linked to financial markets, where rates are currently lower than the rates for subsidized Stafford loans, which doubled to 6.8 percent on July 1.

On a vote of 81 to 18, the U.S. Senate has passed a bipartisan measure brokered with the help of Maine Sen. Angus King that would make it less expensive for college students to borrow money for school this fall.

Under the deal, interest rates would be linked to financial markets, where rates are currently lower than the rates for subsidized Stafford loans, which doubled to 6.8 percent on July 1 after Congress failed to act.

The new deal to lower rates, however, has raised concerns that student loan borrowing could get much more expensive as the economy picks up. But King, an independent, says an important part of the legislation is a cap on rates.

"So that rates for undergraduates can never go above 8.25 percent," he says. "So they've got a cap on the upside. They get the benefit on the downside."

The bill is similar to one the House has already passed. The measure faces more action in Congress.